Strawberries are an important and valuable crop throughout the world. Due to genetic heterozygosity, adaptability, and plasticity of the plant, this species can grow in varied environments throughout the world, from Alaska to South Africa (Martinelli, A. [1992] xe2x80x9cMicropropagation of strawberry (Fragaria spp.)xe2x80x9d In: Biotechnology in Agriculture and Forestry 18:354-370, Springer Verlag, Berlin, W. Germany). The high value of the fruit allows for intensive production methods in many regions.
Florida produced approximately 75 million kilograms of strawberries on 2,350 hectares in the 1993-94 season, an average yield of over 32,000 kg haxe2x88x921 (Freie, R. and N. Pugh [1995] Florida agricultural statistics: Vegetable Summary 1992-1993, Florida Department of Agriculture and Consumer Services, Tallahassee, Fla. p. 47-48). Most of the crop is harvested between December and April with peak production occurring in mid-March. The average value of fruit ranged from greater than $3.00 per kg in November/December declining through the season to less than $1.00 per kg in March/April. However, only 10% of Florida""s strawberry production occurs in November/December when the crop value is highest. Greater than 50% of Florida""s production occurs in March/April when fruit value is below production costs (Smith, S. and T. Taylor [1993] xe2x80x9cProduction cost for selected vegetables in Florida, 1992-93,xe2x80x9d In: University of Florida Circular 1121, Gainesville, Fla. p.22).
Commercial strawberry cultivars must be vegetatively propagated because seeds are not true to type. This propagation has traditionally been done in field nurseries to produce a bare-root transplant. There are many problems associated with these bare-root transplants. However, containerized transplants also have drawbacks including being very vegetative and lacking early fruit production. Researchers have studied different methods for initiating early flower development in containerized plants. For example, researchers have attempted to place containerized plants in large coolers (without light) to initiate flower buds, but this has not been successful.
Many environmental conditions have been shown to affect strawberry plant growth and development during propagation. See, for example Durner, E. F., E. B. Poling, and E. A. Albregts [1987] xe2x80x9cEarly season yield responses of selected strawberry cultivars to photoperiod and chilling in a Florida winter production systemxe2x80x9d J. Amer. Soc. Hort. Sci. 112:53-56; Maas, J. L. [1986] xe2x80x9cPhotoperiod and temperature effects on starch accumulation in strawberry rootsxe2x80x9d Adv. Strawberry Prod. 5:22-24; Long, J. H. [1935] xe2x80x9cSeasonal changes in nitrogen and carbohydrate content of the strawberry plantxe2x80x9d Proc. Amer. Soc. Hort. Sci. 33:386-388 as well as dormancy Bringhurst, R. S., V. Voth and D. VanHook [1960] xe2x80x9cRelationship of root starch content and chilling history to performance of California strawberriesxe2x80x9d Proc. Amer. Soc. Hon. Sci. 75:373-381; and Durner, E. F., J. A. Barden, D. G. Himelrick, and E. B. Poling [1984] xe2x80x9cPhotoperiod and temperature effects on flower and runner development in day-neutral, Junebearing, and Everbearing strawberriesxe2x80x9d J. Amer. Soc. Hort. Sci. 109:396-400.
The subject invention concerns methods for enhancing flower induction in strawberry plants. More specifically, one embodiment of the subject invention provides a method for inducing flowering in strawberry plants by reducing the daytime temperature of the strawberry plants. In a preferred embodiment of the subject invention the daytime temperature may be reduced from about 30xc2x0 C. to about 20xc2x0 C. in order to induce flowering.
In a further embodiment of the subject invention, enhanced flower induction can be obtained according to the subject invention by reducing the amount of daylight (photoperiod) to which the strawberry plant is exposed. For example, if the photoperiod in a particular area is about 12 hours, then this can be reduced to a period of time, such as 6-10 hours, sufficient to enhance flower induction. In using this means to enhance flower induction, it is not necessary to reduce the temperature. Alternatively, with the reduced photoperiod the temperature may be reduced to a lesser extent than when a full photoperiod is used.
The optimal photoperiod and temperature can be readily determined by a person skilled in the art, having the benefit of the instant disclosure, for a particular strawberry plant species in a particular location.